Railway braking apparatus



17, 1936. H. L. BONE' 2,034,557 RAILWAY BRAKING APPARATUS Filed on". 5, 1954 r 4 Sheets-Sheet l 3 76 Source 0 Low Pressure Fluid. ,Soarce q/Higlz 4 A 1 4 Pressure Fluid.

I IN VENT OR 15%0 Herbert L. Barge F 1. HIS ATTORNEY ch 17, 1936. E 2,034,557 RAILWAY BRAKING APPARATUS Filed Oct. 5, 1934 4 Sheets-Sheet 2 To Source Qf Low Pressure To Source 0 16 Pressure High INVENTOR Herbert L. Ba ge 2' Y mm g HIS TTORNEY 17, 1936. H, L. BONE 0 5 RAILWAY BRAKING APPARATUS Filed 001;. 5, 1934 4 Sheets-Sheet 3 To Source of Low Pressure Fluid.

50am of Pressure Fluid.

IN VENTOR 15%9 Herbert L. Bone F 5. HIS ATTORNEY if V H. L. BONE 2934,55?

RAILWAY BRAKING APPARATUS Filed Oct. 5, 1934- 4 Sheets-Sheet 4 INVENTOR Herbert L. Bqne H15 ATTORNEY Patented Mar. 17, 1936 TES PATENT OFFIE RAILWAY BRAKING APPARATUS Application October 5, 1934, Serial No. 747,047

9 Claims.

My invention relates to railway braking apparatus, and particularly to braking apparatus of the type comprising wheel-engaging braking bars located beside a track rail, and movable toward and away from the rail into braking and non-braking positions. More particularly, my invention relates to apparatus of the type described wherein the braking bars are arranged to be moved to their braking positions by means of one or more fluid pressure operated motors, and to be restored to their non-braking positions by a suitable biasing means, such as gravity.

Specifically, my present invention relates to means for controlling the supply of fluid pressure to, and exhaust of fluid pressure from, the fluid pressure motor or motors of braking apparatus of the type described when the braking apparatus is to be utilized in connection with a duplex pressure fluid distribution system such as is disclosed and claimed in Letters Patent of the United States, No. 2,003,034, granted to me on May 28, 1935, and one object of my invention is to improve and simplify the control means disclosed in the said application.

Other objects of my invention will appear as the description proceeds.

I will describe several forms of apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a view, partly sectioned and partly diagrammatic, illustrating one form of apparatus embodying my invention. Figs. 2 and 3 are views, similar to Fig. l, but showing modified forms of the apparatus illustrated in Fig. 1, which modified forms of apparatus also embody my invention. Fig. 4 is a fragmentary view showing an other modified form of the apparatus illustrated in Fig. 1, and also embodying my invention.

Similar reference characters refer to similar parts in each of the several figures.

Referring first to Fig. 1, the reference character I designates one track rail of a stretch of railway track, which track rail, as here shown, is secured to a rail support 2 mounted on an adjacent pair of the usual crossties 3, only one crosst-ie 3 being visible in the drawings. Associated with the rail I is a car retarder comprising two braking bars A and A located on opposite sides of the rail. Each of these braking bars comprises, as usual, a brake beam 4 and a brake shoe 5.

The braking bars are arranged to be moved toward and away from the rail I by means of a lever 6 which is pivotally mounted at One end on a pivot pin 6 carried by the rail support 2, and a lever I which is pivotally mounted intermediate its ends on the pivot pin 8. The lever 6 is inclined upwardly and extends away from the rail I and is provided in its upper surface with a groove 6 which receives the braking bar A The one end I of the lever I is likewise inclined upwardly and extends away from the rail I at the opposite side of the rail from the H lever 6, and the other end. I of the lever I is inclined downwardly and extends away from the rail I below the lever 6. The end I of the lever I is provided in its upper surface with a groove 1, similar to the groove 6 in the lever 6, which groove receives the braking bar A The parts are so proportioned that if the outer or free ends of the levers 6 and I are moved apart, the braking bars will be moved toward the rail I into their effective or braking positions. When the braking bars occupy their braking positions, the brake shoes 5 will engage the opposite side faces of a car wheel traversing rail I, and will retard the speed of the car. The center of gravity of the lever 6 and braking bar A is considerably to the right of the pivot pin 8, so that this lever will normally tend to rotate in a clockwise direction about the pivot pin. Similarly, the center of gravity of the lever 1 and braking bar A is to the left of the pivot pin 8, so that this lever will normally tend to rotate in a counter-clockwise direction about the pivot pin. It will be apparent, therefore, that when no force is applied to the free ends of the levers 6 and I to move them apart, the free ends of these levers will move toward each other, thereby moving the braking bars to their ineffective or non-braking positions in which they are shown in the drawings.

The levers 6 and I are arranged to be moved apart to move the braking bars to their braking positions by means of a fluid pressure motor M comprising a cylinder 9 containing a reciprocable piston III which drives a piston rod II. The cylinder 9 is pivotally connected with the free end of the lever 6 by means of trunnions I2 formed on the side of the cylinder and extending through bifurcations I3 formed on the lever 6, while the piston rod II is connected at its free end with the free end l of the lever I by means of an adjustable eye bolt I4 and a pivot pin I5. Fluid pressure may be admitted to the cylinder 9 between the upper end of the cylinder and the piston I through an opening I6 which is threaded to receive a pipe Ili When fluid pressure is admitted to the cylinder 9 through the pipe I6 and opening I6, the piston II] will be forced downwardly and the cylinder 9 upwardly, thereby separating the levers 6 and I, and hence moving the braking bars toward their effective or braking positions, it being obvious that when the braking bars are moved to their braking positions, they will exert a braking force which is proportionate to the pressure of the fluid supplied to the cylinder 9.

It should be pointed out that while in the drawings I have shown only one operating unit for the braking bars A and A in actual practice these braking bars are provided with a plurality of other similar operating units, disposed at spaced intervals along the bars, substantially as shown in Letters Patent of the United States, No. 1,927,201, granted to me on September 19, 1933, for Railway braking apparatus. It should also be pointed out that, as a general rule, the car retarder will consist not only of braking bars associated with one track rail, as shown in the drawings, but also of similar braking bars associated with the opposite rail as well, the length of the braking bars associated with both track rails being determined by the speed and the weight of the cars to be retarded, the lengths of the cars, the number of wheels on the cars, etc.

The supply of fluid pressure to cylinder 9 is controlled by three main air valves |6, I1 and I8, which main air valves are, in turn, controlled by three electro-pneuinatic pilot valves V V and V The pilot valves V V and V are similar, and each comprises a valve stem 19 biased to an upper position by means of a spring 20, and provided with a winding 2| and an armature 22. When one of the Valves V is energized, valve stem I9 of this valve moves downwardly against the bias exerted by the associated spring 20, and, under these conditions, an associated pipe 23 is connected with a pipe 24. When one of the valves V is deenergized, however, the associated pipe 23 is disconnected from pipe 24 and is connected with atmosphere through a port 25. The pipe 24 forms part of a high pressure distribution system, and is constantly supplied with fluid pressure, usually air, from a relatively high pressure source not shown in the drawings. It follows, therefore, that when one of the valves V is energized, the associated pipe 23 is supplied with fluid pressure from the high pressure system.

The main air valves l6, l1 and |8 are all located in the same valve body 26, and associated with each valve is a spring 21 which constantly biases the valve to an upper or closed position. Formed in the valve body 29 in axial alignment with the valve H5 is a cylinder 28 containing a reciprocable piston 29 which is operatively connected with the valve |fi by a valve stem 30. The upper end of the cylinder 28 is connected with the pipe 23 which is associated with valve V and it will be apparent, therefore, that when valve V is deenergized, so that the associated pipe 23 is connected with atmosphere, the spring 21 associated with valve IE will hold this valve closed and piston 29 in its upper position, but that, when valve V is energized, as shown in the drawings, the fluid pressure which is then supplied to the associated pipe 23 will force piston 29 to its lowermost position, thus opening valve 16. When valve I3 is opened, cylinder 9 of motor M is connected with atmosphere through pipe Hi a chamber 3| formed in valve body 26, a passageway 32, a chamber 33 formed in valve body 26, valve H3, a chamber 34 formed in valve body 26, and a port 35, but when this valve is closed, cylinder 9 is disconnected from atmosphere.

The valve body 25 is also formed with a second cylinder 36 containing a reciprocable piston 31 which is operatively connected with the valve I1 by means of a piston rod 38, and the upper side of which cylinder is connected to the pipe 23 associated with valve V When valve V is energized, the fluid pressure which is then supplied to the associated pipe 23 forces piston 31 to its lowermost position, thereby opening valve l1, and under these conditions cylinder 9 of motor M becomes connected with a pipe 39 through pipe Hi chamber 3|, valve I1, and a chamber 49 formed in valve body 26. Pipe 39 forms part of a low pressure distribution system, and is constantly supplied with fluid pressure, usually air, from a relatively low pressure source not shown in the drawings. It follows, therefore, that when valve V is energized, fluid from the low pressure source will be supplied to cylinder 9. When valve V is deenergized, however, the spring 21 associated with valve |1 moves valve H to its closed position and piston 31 to its upper position, thus disconnecting cylinder 9 from pipe 39, and hence from the low pressure source.

The valve body 26 is further formed with a third cylinder 4| containing a reciprocable piston 42 which is operatively connected with valve l8 by means of a piston rod 43. The cylinder 4| on the upper side of piston 42 is constantly connected with the pipe 23 associated with valve V and it will be apparent, therefore, that when valve V is energized, piston 42 will open valve l8. When valve l8 becomes opened, cylinder 9 becomes connected with pipe 24, and this cylinder is then supplied with fluid from the high pressure distribution system. When valve V is deenergized, however, spring 21 associated with valve I9 closes this valve which, in turn, disconnects cylinder 9 from the high pressure distribution system.

It follows from the foregoing that cylinder 9 will be connected with the high pressure source, the low pressure source, or with atmosphere, according as valves V V or V are energized.

The Valves V are controlled in part by a plurality of pressure responsive devices, each designated by the reference character P with a distinguishing exponent. Referring to the pressure responsive device P for example, this device comprises a Bourdon tube 44 connected with the pipe 23 associated with valve V and subjected to the pressure on the upper side of piston 31. The Bourdon tube 44 controls a contact |545 which is closed at all times except when the pressure on the upper side of piston 31 is equal to or above the pressure at which valve |1 opens. The pres sure responsive devices P P and P are similar to the pressure responsive device P except that the Bourdon tube 44 of each of these devices is connected with the pipe I 6 which communicates with the cylinder 9 of motor M, thus subjecting these devices to the pressure of the fluid in the motor cylinder. The devices P and P are arranged to operate at different pressures as the pressure in cylinder 9 increases. For example, for all pressures below 20 pounds per square inch, contact 4545 of each of these devices is closed. If the pressure exceeds 20 pounds per square inch, contact 4545 of device P opens, and if the pressure exceeds 30 pounds per square inch, contact 45-45 of device P closes. In similar manner, the device P is adjusted to open its contact 4545 at 70 pounds per square inch, and to close its contact 45-45 at 80 pounds per square inch. Of

course, these specific pressures are not essential, but are only mentioned for purposes of illustration.

The Bourdon tube 44 of device 1 is connected by means of a pipe 46 with a reservoir R. which reservoir, in turn, is connected with the pipe 39 by means of a pipe 41. A restricted orifice 48 is provided in the pipe 41, and the function of this restricted orifice and of the reservoir R is to prevent rapid fluctuations which may occur in the low pressure distribution system, of which the pipe 39 forms a part, from being transmitted to the Bourdon tube 35 of the device P The member 55 controlled by the tube 45 of device P is connected mechanically with the member 45 controlled by the tube 44 of device P by means of a link M5, and it will be seen, therefore, that the members 45 of the two devices P and P are constrained to move together, but that, these members oppose each other when fluid pressure is admitted to the associated Bourdon tubes. The contacts 45- l5 and l5l5 controlled by Bourdon tube 35 of device P are so constructed that these contacts cannot become simultaneously closed, and the parts are so proportioned that contact 5 l5 of device P will close when the pressure in the low pressure system exceeds that in the motor cylinder 9 by five pounds per square inch or more, and that contact 4545 of device P will close when the pressure in the cylinder 9 of motor M exceeds that in the low pressure distribution system by five pounds per square inch or more.

The valves V are also controlled by a manually operable lever L, which, as here shown, is capable of assuming five positions, indicated by dotted lines in the drawings, and designated by the reference characters 10 to 11: inclusive. The lever L controls a plurality of contacts, each designated by the reference character 59 with a distinguishing exponent corresponding to the position of the lever in which the corresponding contact is closed. For example, contact 50 is closed in the :0 position of the lever, contact 56 in the p position of the lever, etc.

Lever L will usually be located at a point remote from the braking apparatus, as in the control cabin of a classification yard car retarder system, and will be connected with the braking apparatus by means of line wires extending from the control cabin to the braking apparatus.

The pressure of the fluid in the low pressure system may be maintained at any suitable pres sure, but for purposes of illustration, I will assume that this pressure is maintained at approximately 50 pounds per square inch. Likewise, the pressure of the fluid in the high pressure system may be maintained at any desired pressure, but for purposes of illustration, I will assume that this latter pressure is maintained at approximately pounds per square inch.

As will be explained more fullyhereinaftenfiuid is at times vented from the motor M into the low pressure system, and in order to insure that all of the fiuid in the low pressure system may be used, and also that the compressing of the fluid may be done most efiiciently, it is preferable that the fluid for the high pressure system should be obtained by the use of a compressor which will draw fluid from the low pressure system and compress it to the pressure required for the high pressure system, instead of compressing the fluid directly from atmospheric pressure to the pressure re quired for the high pressure system.

As shown in the drawings, lever L occupies its p or off position, which is the position which is lever normally occupies when no cars are to be retarded, and all of the contacts of lever L with the exception of contact 50 are therefore open. Valves V and V are both deenergized.

Valve V however, is energized over a circuit which passes from a suitable source of current here shown as a battery B, through wires '53, 5 62 and BI, contact 59 of lever L, line wire 55, wire 52, winding 2| of valve V wire 53, contact 45l5 of pressure responsive device P and wires 54 and 55 back to battery B. Since valves V and V are both deenergized, main air valves IT and I8 are both closed, and the supply of fluid pressure to cylinder 9 of motor M from both the high and low pressure distribution systems is therefore cut off; and since valve V is energized, main air valve I 6 is open so that cylinder 9 is connected with atmosphere. The braking bars are therefore held in their ineffective or nonbraking positions by gravity. Contact iii- 55 of each of the pressure responsive devices P P P and P is closed, while contact 4545 of each of the pressure responsive devices P P" and P is open.

In explaining the operation of the apparatus as a whole, I will first assume that the operator wishes to make a comparatively light brake application. To do this, he moves lever L from its p position to its 21 position, thereby opening contact 50 of lever L and closing contact 59 The opening of contact 58 of lever L interrupts the circuit which was previously closed for valve V at this contact, and valve V therefore becomes deenergized and disconnects the associated pipe 23 from pipe 24, and connects the associated pipe 23 to atmosphere, thus permitting spring 27 to close valve l6, and hence disconnecting the region of cylinder 9 of motor M between piston H3 and the upper end of the cylinder from atmosphere. The closing of contact 58 of lever L completes a circuit for valve V and current flows from battery B through wires 13, 64, and 62, contact 50 of lever L, line wire 56, contact l5 l5 of pressure responsive device P wires 51 and 58, winding H of valve V wire 59, and line wire 55 to battery B. Valve V therefore becomes energized and connects the associated pipe 23 with pipe 24. When the associated pipe 23 becomes connected with pipe 24, fiuid pressure is supplied to this pipe 23, and as soon as this pressure increases to 15 pounds per square inch, contact 45-45 and pressure responsive device P opens. The opening of this contact, under these conditions, however, has no effect on the remainder of the apparatus. The pressure supplied to pipe 23 also causes piston 31 to move downwardly and open valve H in the manner previously described, and as was previously pointed out, when valve i'i' be comes opened, pipe Hi becomes connected with pipe 39, so that fluid pressure from the low pres sure system is then supplied to the upper end of cylinder 9 of motor M. The fiuid pressure thus supplied to cylinder 9 forces piston l0 downwardly and cylinder 9 upwardly, thereby moving the braking bars to their braking positions. As soon as the pressure in cylinder 9 increases to 20 pounds per square inch, contact ltlfi of pressure responsive device P opens and interrupts the circuit just traced for valve V Valve V then becomes deenergized and permits valve H to close thus cutting off the supply of fluid pressure to the upper end of cylinder 9 of motor M. Valve V will then remain deen- H ergized until the pressure of the fluid in cylinder 8 has again decreased to 20 pounds per square inch, whereupon contact 415-45 of pressure responsive device P will again become closed, which will reestablish the circuit for valve V thus causing fluid to again be supplied to cylinder 9. If the pressure of the fluid in the upper end of cylinder 9 increases to 30 pounds per square inch for any reason, contact 4545 of pressure responsive device P will become closed, and will complete another circuit for valve V This latter circuit passes from battery B through wires 13, 54 and 62, contact 50 of lever L, line wire 56, contact 45- l5 of pressure responsive device P wires 50 and 52, winding 2| of valve V wire 53, contact 45-45 of pressure responsive device P (which contact is now closed due to the fact that valve V is deenergized), and wires 54 and 55 back to battery B. Valve V will therefore now become energized and will cause valve [6 to open, thus venting fluid from cylinder 9. Valve 15 will continue to vent fluid from cylinder 9 until the pressure in cylinder 9 has decreased to 30 pounds per square inch, at which time contact 55- 15 of pressure responsive device P will open and will deenergize valve V When Valve V becomes deenergized, valve i6 will reclose and will prevent further escape of fluid from cylinder 9. It will be seen, therefore, that when lever L occupies its p position, the braking bars will be held in their braking positions by a pressure of between 20 to 30 pounds per square inch.

If the operator desires to make a more powerful brake application, he will move lever L to its p position. This movement of lever L will interrupt all of the previously traced circuits for valves V and V and will complete another circuit for valve V which latter circuit passes from battery B, through wires 13 and 54, contact 55 of lever L, line wire 63, wires 51 and 58, winding 2i of valve V wire 59, and line wire 55 back to battery B. -It will be noted that this latter circuit is controlled solely by contact 55 of lever L, so that when this circuit becomes closed it will remain closed as long as lever L remains in its 23 position. When this circuit becomes closed, valve V will of course become energized, thus causing both contact Ail-45 of pressure responsive device P to open and valve I! to open. The opening of contact 4545* of pressure responsive device P under these conditions has no effeet on the remainder of the apparatus. When valve ll becomes opened, fluid pressure is admitted to cylinder 9 of motor M from the low pressure distribution system, and since valve V remains energized as long as lever L remains in its p position, it follows that when lever L occupies its 19 position, the pressure in cylinder 9 of motor M will build up to the full pressure of the low pressure system. When the pressure in cylinder 9 has built up to within five pounds of that in the low pressure system, contact 55-45 of pressure responsive device P will open, but the opening of this contact will likewise have no effect on the remainder of the apparatus as long as lever L remains in its 11 position.

If a still higher braking force is desired, the operator will move lever L to its p position. When he does this, if the pressure in cylinder 9 of motor M is more than 5 pounds less than the pressure in the low pressure system, so that contact %555 of pressure responsive device P is closed, as will be the case if lever L previously occupied its 29 or p position, valves V and V will become simultaneously energized, the circuit for valve V under these conditions, passing from battery B through wire 13, contact 55 of lever L, line wire 65, contact 55-45 of pressure responsive device P wire 55, contact l555 of pressure responsive device P wires 61 and 58, winding 2| of valve V wire 59, and line wire 55 back to battery B; and the circuit for valve V passing from battery B through wire 13, contact 55 of lever L, line wire 65, contact 115- 35 of pressure responsive device F wires 66 and 68, winding 2| of valve V wires 69 and 53, contact l5 l5 of pressure responsive device P wire 54, and line wire 55 back to battery B.- The energization of valves V and V will cause fluid pressure to be admitted to the associated cylinders 36 and H, but before the pressure in these cylinders can build up to a pressure which is suificient to cause either valve l! or valve I8 to open, contact 55- 35 of pressure responsive device P will open, and will interrupt the circuit for valve V thus deenergizing this valve. It will be seen, therefore, that when lever L is first moved to its p position from its or 11 position, valve I! will open, but valve 18 will remain closed, so that only fluid from the low pressure system will be admitted to cylinder 9. As soon, however, as the pressure in cylinder 9 has built up to within pounds of the pressure in the low pressure system, contact 15-55 of pressure responsive device P will open and will deenergize valve V thus causing valve I! to close, and also causing contact 55-55 of pressure responsive device P to close. When contact 35-45 of pressure responsive device P now becomes closed, it will re-establish the circuit for valve V and this valve will then become energized and will cause valve E8 to open, thus causing fluid from the high pressure system to be supplied to cylinder 9 of motor M. If, however, when lever L is moved to its 10 position, the pressure in cylinder 9 of motor M, instead of being more than 5 pounds less than that in the low pressure system as just described, is within 5 pounds of that in the low pressure system, as will be the case if the lever previously occupied its p position, valve V will immediately become energized by virtue of the same circuit which causes this valve to become energized when the lever is moved to its p position from its 10 or 1) position, so that under these latter conditions fluid will be immediately supplied to cylinder 9 from the high pressure system. It follows that, when lever L is moved to its 10 position, if the pressure of the fluid in the motor is more than 5 pounds below that in the low pressure system, fluid will be admitted to the motor from the low pressure system until the pressure in the motor builds up to within 5 pounds of that in the low pressure system, after which fluid will be admitted to the motor from the high pressure system. When lever L occupies its 12 position, and the pressure in cylinder 9 of motor M has increased to 70 pounds per square inch, contact 55- 35 of the pressure responsive device P will open and will deenergize valve V and if the pressure increases to 80 pounds per square inch, contact 4545 of pressure respcnsive device P' will become closed, and will simultaneously complete circuits for valves V and V The circuit which is completed for valve V passes from battery B, through wire 73. contact 55 of lever L, line wire 55, contact 4545 of pressure responsive device 1 wires H, 12, 50 and 52, winding 2! of valve V wire 53, contact l545 of pressure responsive device P wire 55, and line wire 55 back to battery B. The circuit which is completed for valve V passes from battery B, through wire 73, contact 50 of lever'L, line wire 65, contact 45-55 of pressure responsive device P wire 1 l, asymmetric U in its low resistance direction, contact 45fi5 of pressure responsive device P wires 61 and 58, winding 21 of valve V wire 59, and line wire 55 back to battery B. The simultaneous energization of valves V and V will cause fluid to be simultaneously admitted to the associated cylinders 23 and 38, but before the pressure in cylinder 28 can build up to that at which valve i6 opens, contact 45-fi5 of pressure responsive device P will open and will deenergize valve V thus causing fluid which was previously supplied to cylinder 28 to be vented to atmosphere. It will be seen therefore that valve ll will open, but valve IE will remain closed. The opening of the valve i! will connect cylinder 9 of motor M with the low pressure distribution system, and since the pressure in the cylinder is considerably above that in the low pressure system, fluid will be vented into the low pressure system. Fluid will continue to be vented into the low pressure system until the pressure again decreases below 80 pounds per square inch, at which time contact 45-45 of pressure responsive device P will open and deenergize valve V thus causing valve I T to close and disconnect cylinder 9 from the low pressure distribution system.

If the operator moves lever L to its 11 position from its 11 or 17 position, when the lever reaches its 11 position, contact 4545 of pressure responsive device P will be closed for reasons which will be apparent from the foregoing description, and under these conditions valves V and V will become simultaneously energized. The circuit for valve V under these conditions passes from battery B through contact 58 of lever L, line wire '14, wire 66, contact Q5- i5 of pressure responsive device P wires 5'! and 58, winding 2| of valve V wire 59 and line wire 55 back to battery B. The circuit for valve V under these conditions passes from battery B, through contact 59 of lever L, line wire M, wire 68, winding 2| of valve V wires 59 and 53, contact it- 55 of pressure responsive device P wire 54, and line wire 55 back to battery B. As soon as valve V becomes energized, and the pressure in the associated pipe 23 has built up to 15 pounds per square inch contact 35-45 of pressure responsive device P will open, and will interrupt the circuit just traced for valve V so that this valve will become deenergized. Valve V however, will remain energized and will cause valve I! to open, thus causing fluid pressure from the low pressure system to be supplied to cylinder 9 of. motor M. When the pressure in cylinder 9 has built up to within 5 pounds of that in the low pressure system, contact 45-45 of pressure responsive device P will open and will dc energize valve V thus causing valve ii to close and contact l5-i5 of pressure responsive device P to also close. When valve I '5 becomes closed, the supply of fluid pressure to cylinder 9 of motor M from the low pressure system will, of course, be cut oil. The closing of contact i 35 of pressure responsive device P will reestablish the circuit last traced for valve V and this valve will therefore become energized, thus causing valve Hi to open and admit fluid pressure to cylinder 9 of motor M from the low pres sure system. Valve V will now remain energized as long as the lever remains in its 10 position, and it will be apparent, therefore, that the braking bars will continuously exert their maximum braking force under these conditions.

If the operator instead of moving lever L to its 11 position from its p or 23 position, moves the lever to its position from its p or 11 position, contact 45-45% of pressure responsive device P will be open when the lever reaches its position, and, under these conditions, valve V will immediately become energized, so that fluid pressure will immediately be supplied to cylinder 9 of motor M from the high pressure system.

I will now assume that the operator has moved lever L to its 11 position to cause the braking bars to exert their maximum braking force, and that he wishes to restore the braking bars to their ineffective or non-braking position. To do this, he will move lever L from its 11 position to its p position. When he does this, the circuit which was previously closed for valve V at contact 50 of lever L will become interrupted and valve V will therefore become deenergized and will disconnect cylinder 9 of motor M from pipe 26, so that the supply of fluid pressure to cylinder 5 from the high pressure system will then be cut on. Furthermore, when the operator moves lever L to its p position, contact @5-45 of pressure responsive device P will be closed since the pres sure in the motor cylinder will then be more than 5 pounds greater than that in the low pressure system, and as a result, a circuit will be completed for valve V which circuit passes from battery B through wires 13, 64, t2 and 6!, contact 56 of lever L, line wire 5!, wires til and H2, asymmetric unit U in its low resistance direction, contact 45- i5 of pressure responsive device P wires 8? and 58, winding 2! of valve V Wire 59, and line wire 55 back to battery B. A circuit will also be simultaneously closed for valve V which circuit may be traced from battery B through wires l3, Fi l, 62, and 6!, contact 59 of lever L, line wire 5i, wire 52, winding 25 of valve V wire 53, contact 4545* of pressure responsive device P wire and line wire 55 back to battery B. Valves V and V will therefore both become energized. As soon as valve V becomes energized, however, contact 45 l5 of pressure responsive device P will open, and will interrupt the circuit just traced for valve V thus causing this valve to become immediately deenergized. The energization of valve V will, of course, cause valve 5? to open, and since the pressure in cylinder 9 of motor M is above that in the low pressure system, fluid from the motor will be vented into the low pressure system. When the pressure in the motor has decreased to within five pounds of that in the low pressure system, contact l i5 of pressme responsive device P will open and will deenergize valve V and when valve V becomes deenergized, valve I? will close, and contact 55-d5 of pressure responsive device P will also close. The closing of valve ll will disconnect motor M from the low pressure system, while the closing of contact t5ili of pressure responsive device P will re-establish the circuit for valve V Valve V will therefore become energized and will cause valve 55 to open, thus venting the remainder of the fluid in cylinder 9 of motor M to atmosphere. As the fluid in cylinder 9 of motor M is vented to atmosphere, the braking bars will return to their inefiective or non-braking positions by gravity, and when the braking bars have reached their full non-braking positions all parts will be restored to their normal positions in which they are illustrated in the drawings.

It will be seen, therefore, that when lever L is moved from its position to its p position to restore the braking bars to their non-braking positions, the fluid which was previously supplied to cylinder 9 of motor M will be vented into the low pressure distribution system until the pressure decreases to Within 5 pounds of that in the low pressure system after which the remainder of the fluid will be vented to atmosphere, thus effecting a considerable saving in the amount of fluid pressure required over that which would be required if all of the fluid supplied to motor M were vented to atmosphere.

If the operator instead of moving lever L from its 12 position to its 10 position, moves the lever from its 10 position to its p position, valve V will become energized over a circuit which passes from battery B through wires 13, 64 and 62, contact 59 of lever L, line wire 55, contact 4545 of pressure responsive device P wire 12, asymmetric unit U in its low resistance direction, contact 4545 of pressure responsive device P wires 6'! and 58, winding 2| of valve V Wire 59, and line wire 55 back to battery B. Valve V will also become simultaneously energized over the previously described circuit for this valve including contact 15-45 of pressure responsive device P As soon as valve V becomes energized, however, contact 45---45 of pressure responsive device P will open and will deenergize valve V The energization of valve V will of course cause valve I! to open, and when this valve opens, since the pressure of the fluid in cylinder 9 is then above that in the low pressure system, fluid will be vented from cylinder 9 into the low pressure system. As soon as the pressure in cylinder 9 has decreased to within 5 pounds per square inch of that in the low pressure system, contact 4545 of pressure responsive device P will open and will deenergize valve V thus causing valve I! to close, and contact 35-45 of pressure responsive device P to also close. When valve H becomes closed, cylinder 9 becomes disconnected from the low pressure system, and when contact 45--45 of pressure responsive device P becomes closed, valve V becomes energized and opens valve l6, thus causing fluid to be vented from cylinder 9 to atmosphere. When the pressure of the fluid in cylinder 9 has decreased to 30 pounds per square inch, contact 4545 of pressure responsive device P will open, and will deenergize valve V and the fluid in cylinder 9 will subsequently be maintained at a pressure of between 20 and 30 pounds in the same manner as whenlever L is moved to its 17 position from its p position. It will be seen, thereforepthat under the conditions just described, the fluid in cylinder 9 will be vented into the low pressure distribution system until the pressure decreases to substantially the pressure of the low pressure system, after which the fluid in cylinder 9 will be vented to atmosphere, until the pressure decreases to that corresponding to the 11 position of the lever.

While in the foregoing I have described the operation of the apparatus for only a few of the possible movements of lever L, the operation of the apparatus for the remainder of the movements of lever L is similar to that already described, and it is believed, therefore, that this additional operation will be understood from an inspection of the drawings and from the foregoing without the necessity for describing it in detail here.

One function of the asymmetric unit U is to prevent improper operation of the valves controlled by the pressure responsive device P in the event that the contact points 45* and 4.":

become short-circuited due to the presence of moisture, or for any other reason.

Referring now to Fig. 2, the apparatus here shown is similar to that shown in Fig. 1, with the exception that the circuits for controlling the valves V have been modified somewhat, and asymmetric units have been employed in some of these circuits, to decrease the number of line wires required between the control point and the car retarder.

The operation of the apparatus shown in Fig. 2 is as follows: When lever L occupies its 10 or off position, valves V and V are both deenergized, and valve V is energized over a circuit which passes from a battery B through line Wire 80, wire 8|, contact 45l-5 of pressure responsive device P wire 82, winding 2| of valve V wire 83, an asymmetric unit U in its low resistance direction, line wire 84, wire 85, and contact 50 of lever L back to battery B. Since valves V and .V are deenergized valves l1 and I8 are closed, and the supply of fluid pressure to cylinder 9 of motor M from both the low and high pressure distribution systems is therefore cut oil and since valve V is deenergized, valve I6 is open, so that cylinder 9 of motor M is connected to atmosphere. The braking bars are therefore held in their non-braking positions by gravity.

If, now, lever L is moved to its 11 position, valve V will become deenergized, and valve V will become energized over a circuit which passes from battery 13 through line Wire 89, wire 89, winding 2! of valve V contact l5 l5 of pressure responsive device P line Wire 8?, and contact 50 of lever L back to battery B The deenergization of valve V will cause valve I6 to close and disconnect cylinder 9 of motor M from atmosphere, while the energization of valve V will cause valve I! to open and connect cylinder 9 with pipe 39, so that fluid pressure will then be supplied to cylinder 9 from the low pressure distribution system, thus causing the braking bars to move to their braking positions. When the pressure of the fluid in cylinder 9 increases to 20 pounds per square inch, contact l5 l5 of pressure responsive device P will open and will deenergize valve V thus causing valve I! to close and disconnect cylinder 9 from the low pressure distribution system; and if the pressure of the fluid in cylinder 9 increases to 30 poundsper square inch, contact 4545' of pressure responsive device P will become closed, and will complete another circuit for valve V which latter circuit passes from battery B through line wire 80, wire 8|, contact div-45 of pressure rcsponsive device P wire 82, winding 2| of valve V wire 83'. asymmetric unit U in its low resistance direction, contact 4545 of pressure responsive device P line wire 87, and contact 59 of lever L back to battery B Valve V will therefore become energized and will cause valve 59 to open, so that fluid will then be vented to atmosphere. Valve I6 will continue to vent fluid from cylinder 9 to atmosphere until the pressure in the cylinder again decreases to 30 pounds per square inch, at which time contact ii-45 of pressure responsive device P will open and will deenergize valve V thus causing valve It to close. It will be seen, therefore, that with the apparatus shown in Fig. 2, when lever L is moved to its 17 position, the braking bars will be held in their braking positions by a pressure of between 20 to 30 pounds per square inch in the same manner as with the apparatus shown in Fig. 1.

If lever L is moved from its 10 position to its p position, the circuit last traced for valve v will become interrupted, and another circuit for valve V will become closed. This latter circuit passes from a battery B through contact 50 of lever L, line wire 84, asymmetric unit U in its low resistance direction, wires 88 and 89, winding 2! of valve V wire 86, and line wire 89 back to battery B The energization of valve V by virtue of the circuit just traced will of course cause valve ll to open and admit fluid to cylinder 9 of motor M from the low pressure distribution system. It will be noted that the circuit over which valve V is energized under these conditions is controlled entirely by contact 59 of lever L, and it follows therefore that valve V will now remain energized as long as lever L remains in its 93 position, and the braking bars will therefore be held in their braking positions under these conditions by fluid at the full pressure of the low pressure distribution system. It should be pointed out that when the pressure of the fluid in cylinder 9 increases to within five pounds of that in the low pressure system, contact i45 of pressure responsive device P will open, but the opening of this contact will have no effect on the remainder of the apparatus as long as lever L remains in its position.

I will next assume that lever L is moved from its p position to its p position. Under these conditions valve V will become deenergized and valve V will become energized, thus causing fluid pressure to be supplied to the upper end of cylinder 9 from the high pressure system. The circuit over which valve V becomes energized under these conditions passes from battery B through line wire 89, wire 8|, contact GEL-45 of pressure responsive device P wires 82 and 99, winding 2| of valve V Wires 9| and 92, contact 65-45 of pressure responsive device P line wire 93, contact 59 of lever L, and wire 94 back to battery B When the pressure of the fluid in the upper end of cylinder 9 becomes more than five pounds greater than that in the low pressure dis-' tribution system, contact 4545 of pressure responsive device P will close, but the closing of this contact under these conditions will have no' effect on the remainder of the apparatus. When the pressure in the upper end of cylinder 9 increases to '70 pounds per square inch, contact 45-45 of pressure responsive device 1 will open and will deenergize valve V thus causing the supply of fluid pressure to cylinder 9 from the high pressure distribution system to be cut off. If the pressure in the upper end of cylinder 9 increases to 80 pounds per square inch for any reason, contact i5-45 of pressure responsive device P will close, and will simultaneously complete circuits for valves V and V The circuit which is completed for valve V passes from battery B through line wire 85, wire 8!, contact 45-45 of pressure responsive device P wire 82, winding 2| of valve V wire 83, asymmetric unit U in its low resistance direction, contact id5 of pressure responsive device P line wire 93, contact 59 of lever L, and Wire 9 back to battery B The circuit which is completed for valve V passes from battery B through line wire 80, wire 95, winding 2! of valve V wires 39, 89 and 95, contact 4545 of pressure responsive device P asymmetric unit U in its low resistance direction, contact 45-45" of pressure responsive device P line wire 93, contact 59 of lever L, and wire 94 back to battery B The simultaneous energization of valves V and V will cause. fluid pressure to be simultaneously supplied to cylinders 28 and 36, but before the pressure in cylin- '7 der 28 can build up sufliciently to cause valve Hi to open contact l-545 of pressure responsive device P will open and will interrupt the circuit which was previously closed for valve V thus cutting on the supply of fluid pressure to cylinder 28. Valve l1, however, will open and will connect cylinder 9 with the low pressure distribution system, and since the pressure in cylinder 9 is then above that in the low pressure system fluid will be vented into the low pressure system. Fluid will continue to be ve-ntedinto the low pressure system until the pressure again decreases below 80 pounds per square inch, at which time contact 45-45 of pressure responsive device P will open and will deenergize valve V thus causing valve H to reclose and disconnect cylinder 9 from the low pressure system.

If lever L, instead of being moved to its 10 position from its 10 position, is moved to its p .position directly from its p or 10 position, contact flit-45 of pressure responsive device P will be closed when the lever L reaches its p position, and under these conditions valve V will become energized over the circuit previously traced, and valve V will also become energized over a circuit which passes from battery B through line wire 89, wire 89, winding 2| of valve V wires 89, 88 and 95, contact NF-45 of pressure responsive device P wires 96 and 92, contact 4545* of pressure responsive device P line wire 93, contact 59 of lever L, and wire 94 back to battery 13 As soon as valve V becomes energized, however, contact 45l5 of pressure responsive device P will open and will deenergize valve V so that only valve V will remain energized. The energization of valve V will cause fluid pressure tobe supplied to cylinder 9 of motor M from the low pressure system until the pressure increases to within five pounds of that in the low pressure system, at which time contact 45- l5 of pressure responsive device P will open and will deenergize valve V thus causing the supply of fluid pressure to cylinder 9 from the low pressure system to be cut off. As soon as valve V becomes deenergized contact l545 of pressure responsive device P will close, and when this contact becomes closed, the circuit which was previously closed for valve V will be re-established, and the operation of the apparatus from this point on will be the same as was previously described when lever L was moved from its p position to its p position.

If lever L is moved to its p position or its p position long enough to permit the pressure in the upper end of cylinder 9 of motor M to build up to the pressure at which contact 4545 of pressure responsive device P opens, and the lever is then moved to its 10 position, valve V will immediately become energized and will subsequently remain energized as long as the lever remains in its 10 position by virtue of a circuit which passes from battery B through contact 59 of lever L, line wire 93, an asymmetric unit U in its lower resistance direction, wire 9|, winding 2| of valve V wires 90 and 82, contact 45- i5 of pressure responsive device P wire 8|, and line wire 80 back to battery B When valve V becomes energized, fluid pressure will, of course, be supplied to cylinder 9 of motor M from the high pressure distribution system, and it will be apparent, therefore, that. under these conditions motor M will be constantly supplied with fluid pressure from the high pressure system as long as the lever remains in its 10 posi-- tion. If, however, lever L instead of being moved to its 21 position from its 11 or 12 position in the manner just described is moved to its 11 position directly from its p or p position, so that contact 45-45 of pressure responsive device P is still closed when the lever reaches its p position, valve V will become energized over the circuit last traced for this valve, and valve V will simultaneously become energized over a circuit which passes from battery B through contact of lever L, line wire 93, asymmetric unit U in its lower resistance direction, wire 96, contact -i5- l5 of pressure responsive device P wires 95, 88 and 89, winding 2| of valve V wire 86, and line wire 80 back to battery B The energization of valve V will cause contact l5 l5 of pressure responsive device P to open before valve I8 opens, and when contact 45-45 of pressure responsive device P opens, the circuit over which valve V was previously energized will become interrupted, thus deenergizing this valve. Valve V however, will remain energized and will cause valve I! to open and admit fluid pressure to cylinder 9 of motor M from the low pressure distribution system until the pressure in the motor increases to within five pounds of that in 'the low pressure system, at which time contact i545 of pressure responsive device P will open and will deenergize valve V The deenergization of valve V will, of course, cause the further supply of fluid pressure to cylinder 9 of motor M from the low pressure distribution system to be cut off, and will also cause contact l5 l5 of pressure responsive device P to close. As soon as contact 4545 of pressure responsive device P becomes closed, the circuit over which valve V was previously energized will become reestablished, and the operation of the apparatus will then be the same as when lever L is moved to its 1 position from its 12 or p position. As soon as the pressure in cylinder 9 of motor M has reached a value which is more than five pounds greater than that in the low pressure system, contact 45-45 of pressure responsive device P will close, but the closing of this contact under these conditions will have no effect on the remainder of the apparatus as long as the lever remains in its 12 position.

If, after lever L has been moved to its 11 position, the lever is moved to its 11 position, valve V will become deenergized and valves V and V will simultaneously become energized. The circuit over which valve V becomes energized under these conditions passes from battery B through line wire 89, wire 86, winding 2| of valve V wires 89, 88 and 95, contact 4545 of pressure responsive device P asymmetric unit U in its low resistance direction, contact l545 of pressure responsive device P line wire 81, and contact 59 of lever L back to battery B The circuit over which valve V becomes energized under these conditions is the same as the circuit over which this valve becomes energized when lever L is moved to its p position fromits 12 position, and the pressure in cylinder 9 of motor M increases to more than 30 pounds per square inch. The energization of valve V under these conditions will cause contact 15- of pressure responsive device P to open, and as soon as this contact opens, the circuit over which valve V was previously energized will become interrupted so that valve V will immediately become deenergized. The energization of valve V will also cause valve I! to open, and since the pressure of the fluid in cylinder 9 of motor M is now above that in the low pressure distribution system, fluid will be vented from cylinder 9 into the low pressure distribution system. When the pressure in cylinder 9 of motor M decreases to within five pounds of that in the low pressure distribution system, contact 45-45 of pressure responsive device P will open and will deenergize valve V thus causing valve I! to close and disconnect cylinder 9 from the low pressure distribution system. The deenergization of valve V will also cause contact 45-45 of pressure responsive device P to close and the closing of this contact, in turn, will re-establish the circuit for valve V thus causing valve IE to open and vent fluid from cylinder 9 to atmosphere. When the pressure in cylinder 9 has decreased to 30 pounds per square inch contact 45- 15 of pressure responsive device P will open and will deenergize valve V and the pressure of the fluid in cylinder 9 of motor M will then be maintained at a value of between 20 and 30 pounds per square inch in the same manner as when lever L is moved to its 10 position from its 11 position.

I will now assume that lever L occupies its p position, and that the operator moves the lever directly to its 10 position. Under these conditions, when the lever reaches its 10 position, contact 4545 of pressure responsive device P will be closed, and a circuit will therefore be completed for valve V which may be traced from battery B through line wire 89, wire 86, winding 2i of valve V wires 89, 88 and 95, contact 4545 of pressure responsive device P asymmetric unit U in its low resistance direction, line wire 84, wire 85, and contact 59 of lever L back to battery B The circuit previously traced for valve V including contact 50 of lever L will also become simultaneously closed under these conditions, but as soon as valve V becomes energized, the resultant opening of contact 45-45 of pressure responsive device P will interrupt this circuit for valve V and valve V will therefore immediately become deenergized. The energization of valve V will cause cylinder 9 of motor M to become connected with the low pressure distribution system, and fluid will therefore be vented into the low pressure distribution system until the pressure in the motor decreases to within flve pounds of that in the low pressure system, at which time contact 4545 of pressure responsive device P will open and will deenergize valve V When valve V becomes deenergized, valve I? will close and will disconnect cylinder 9 from the low pressure system. Furthermore, when valve V becomes closed, contact 45-45 of pressure responsive device P will close, and will re-establish the circuit for valve V Valve V will therefore become energized and will cause valve IE to open, thus venting the remainder of the fluid in cylinder 9 to atmosphere. As the pressure in the upper end of cylinder 9 decreases, the braking bars will return to their non-braking positions by gravity, and when the braking bars reach their non-braking positions, all parts will be restored to their normal positions in which they are shown in the drawings.

Referring now to Fig. 3, the apparatus here shown is similar to that shown in Fig. 1 with the exception that the pressure responsive device P has been replaced by a relay A which is connected in multiple with the winding 2| of valve V and which therefore becomes energized whenever the valve V becomes energized. Relay A is provided with a contact I99 which opens whenever this relay becomes energized, and this contact performs the same functions which the contact 45-415 of the pressure responsive device P shown in Fig. l performs.

The operation of the apparatus shown in Fig. 3 is similar to that shown in Fig. 1, and it is believed that this operation will be readily understood from the foregoing description, and from an inspection of the drawings, without describing it in detail.

Referring now to Fig. 4, the portion of the apparatus here shown is likewise similar to the corresponding portion of the apparatus shown in Fig. 1, with the exception that the pressure responsive device P has again been eliminated, and a contact llll has been provided which contact is mechanically connected to the armature 22 of valve V in such manner that this contact will be closed or opened according as valve V is deenergized or energized. The contact lGl performs the same functions as the contact 45--- l5 of the pressure responsive device P shown in Fig. 1 and the operation of the apparatus shown in Fig. 4 is similar in all respects to that shown in Fig. 1.

It should be noted that while I have shown the relay A in Fig. 3, and the contact IOI in Fig. 4 associated with a circuit arrangement for controlling the valves V similar to that shown in Fig. 1, these parts could equally well be used in connection with the circuit arrangement shown in Fig. 2 for controlling these valves, and similar operation of the apparatus in both cases would result.

Although I have herein shown and described only a few forms of railway braking apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. Railway braking apparatus comprising a braking bar extending parallel to a track rail, a fluid pressure motor for moving said braking bar toward said track rail to a braking position, a first pipe connected with a source of relatively low pressure fluid, a second pipe constantly connected with a. source of relatively high pressure fluid, two pressure responsive devices, one subjected to the pressure of the fluid in said first pipe and the other subjected to the pressure of the fluid in said motor, a contact controlled jointly by said two devices in such manner that said contact will be closed when the pressure in said motor is below a predetermined pressure which is less than the pressure in said first pipe and will be open at all other times, and means controlled by said contact for connecting said motor with said first or said second pipe.

2. Railwas braking apparatus comprising a braking bar extending parallel to a track rail, a fluid pressure motor for moving said braking bar toward said track rail to braking positions, a first pipe connected with a source of relatively low pressure fluid, a second pipe connected with a source of relatively high pressure fluid, two pressure responsive devices one subjected to the pressure of the fluid in said first pipe and the other subjected to the pressure of the fluid in said motor, two magnet valves, means controlled by the one valve for connecting said first pipe with said motor, means controlled by the other valve for connecting said second pipe with said motor, a contact controlled jointly by said two devices in such manner that said contact will be closed when the pressure in said motor is below a predetermined pressure which is less than the pressure in said first pipe and will be open at all other times, and means controlled by said contact for selectively controlling said two valves.

3. Railway braking apparatus comprising a braking bar extending parallel to a track rail, a fluid pressure motor for moving said braking bar toward said track rail to a braking position, a first pipe connected with a source of relatively low pressure fluid, a second pipe connected with a source of relatively high pressure fluid, two pressure responsive devices one subjected to the pressure of the fluid in said first pipe and the other subjected to the pressure of the fluid in said motor, a first contact controlled jointly by said two devices in such manner that said contact will be closed when the pressure in said motor is below a predetermined pressure which is less than the pressure in said first pipe and open at all other times, a first magnet valve effective when energized for connecting said first pipe with said motor, a second magnet valve effective when energized for connecting said second pipe with said motor, a second contact which is closed or open according as said first valve is deenergized or energized, means controlled by said first contact for controlling said first magnet valve, and means controlled by said second contact for controlling said second magnet valve.

4.. Railway braking apparatus comprising a braking bar extending parallel to a track rail, a fluid pressure motor for moving said braking bar toward said track rail to a braking position, a first pipe connected with a source of relatively low pressure fluid, a second pipe connected with a source of relativey high pressure fluid, two Bourdon tubes one subjected to the pressure of the fluid in said first pipe and the other subjected to the pressure of the fluid in said motor, said tubes being mechanically connected together in such manner that when pressure is supplied to said tubes they will exert opposing forces on the connecting member, a contact controlled by said two Bourdontubes in such manner that said contact will be closed when and only when the pressure in said motor is below a predetermined pressure which is less than the pressure in said first pipe, a first magnet valve, means controlled by said first magnet valve for connecting said first pipe with said motor, a second magnet valve, means controlled by said second magnet valve for connecting said second pipe with saidmotor, a second contact which becomes opened whenever said first valve becomes energized, means controlled by said first contact for controlling said first magnet valve, and means controlled by said second contact for at times controlling said second magnet valve.

5. Railway braking apparatus comprising a braking bar extending parallel to a track rail, a fluid pressure motor for moving said braking bar toward said track rail to a braking position, a first pipe connected with a source of relatively low pressure fluid, a second pipe connected with a source of relatively high pressure fluid, a first Bourdon tube connected tosaid first pipe through a reservoir and a restricted orifice. whereby said first tube is subjected to the pressure in said first pipe but not to sudden variations in the pressure in said first pipe, a second Bourdon tube subjected to the pressure in said motor, means for mechanically connecting said Bourdon tubes together in such manner that when said tubes are both sub-' jected to fluid pressure they will exert opposing forces on the connecting member, a contact controlled by said tubes in such manner that said contact will be closed when and only when the pressure in said motor is below a predetermined pressure which is less than the pressure in said first pipe, and means controlled by said contact for selectively connecting said pipes with said motor.

6. Railway braking apparatus comprising a braking bar extending parallel to a track rail, a fluid pressure motor for moving said braking bar toward said track rail to a braking position, a first pipe connected with a source of relatively low pressure fluid, a second pipe connected with a source of relatively high pressure fluid, two Bourdon tubes one subjected to the pressure of the fluid in said first pipe and the other subjected to the pressure of the fluid in said motor, said tubes being mechanically connected together in such manner that when pressure is supplied to said tubes they will exert opposing forces on the connecting member, a first contact controlled by said two Bourdon tubes in such manner that said first contact will be closed when and only when the pressure in said motor is below a predetermined pressure which is less than the pressure in said first pipe, a first magnet valve, means controlled by said first contact for at times energizing said first magnet valve, means efiective when said first magnet valve is energized for connecting said motor with said first pipe, a third Bourdon tube subjected to the pressure in said second pipe when said first magnet valve be comes energized, a second contact controlled by said third Bourdon tube and arranged to become opened when said third tube becomes subjected to the pressure in said second pipe, a second magnet valve, means for at times energizing said second magnet valve. when said second contact is closed, and means effective when said second magnet valve becomes energized for connecting said motor with said second pipe.

7. Railway. braking apparatus comprising a braking bar extending parallel to a track, rail, a fluid pressure motor for moving said braking bar toward said track rail to a braking position, a first pipe connected with a source of relatively low pressure fluid, a second pipe connected with a source of relatively high pressure. fluid, two Bourdon tubes one subjected to the pressure of the fluid in said first pipe and the other subjected to the pressure of the fluid in said motor, said tubes being mechanically connected together in such manner that when pressure is supplied to said tubes they will exert opposing forces on the connecting member, a first contact controlled by said two Bourdon tubes in such manner that said first contact will be closed when and only when the pressure in said motor is below a, predetermined pressure which is less than thepressure in said first pipe, a first magnet valve, means controlled by said first contact for at times ener-. gizing said first magnet valve, means; effective when said first magnet valve is energized for connecting said motorwith said first pipe, a third;

becomes energized for connecting said motor with said second pipe, a third contact controlled by said two Bourdon tubes which are connected together and arranged to become closed when and only when the pressure in said motor is above a predetermined pressure which is greater than the pressure in said first pipe, and means controlled by said third contact for at times energizing said first magnet valve.

8. Railway braking apparatus comprising a braking bar extending parallel to a track rail, a fluid pressure motor for moving said braking bar toward said track rail to a braking position, a first pipe connected with a source of relatively low pressure fluid, a second pipe connected with a source of relatively high pressure fluid, two Bourdon tubes one subjected to the pressure of the fluid in said first pipe and the other subjected to the pressure of the fluid in said motor, said tubes being mechanically connected together in such manner that when pressure is supplied to said tubes they will exert opposing forces on the connecting member, a first contact controlled by said two Bourdon tubes in such manner that said first contact will be closed when and only when the pressure in said, motor is below a predetermined pressure which is less than the pressure in said first pipe, a first magnet valve, means controlled by said first contact for at times energizing said first magnet valve, means effective when said first magnet valve is energized for connecting said motor with said first pipe, a relay connected in multiple with said first magnet valve and provided with a contact which becomes open when said relay becomes energized, a second magnet valve,

meansfor at times energizing said second magnet valve when the contact of said relay is closed, and means effective when said magnet valve becomes energized for connecting said motor with. said second pipe.

9. Railway braking apparatus comprising a braking bar extending parallel to a track rail, a fluid pressure motor for moving said braking bar toward said track rail to a braking position, a

first pipe connected with a source of relatively low pressure fluid, a second pipe connected with a source of relatively high pressure fluid, two Bourdon tubes one subjected to the pressure 01 the fluid in said first pipe and the other subjected to the pressure of the fluid in said motor, said tubes being mechanically connected together in such manner that when pressure is supplied to said tubes they will exert opposing forces on the connecting member, a first contact controlled by said two Bourdon tubes in such manner that said first contact will be closed when and only when the pressure in said motor is below a. predetermined pressure which is less than the pressure in said first pipe, a first magnet valve, means controlled by said first contact for at times energ1zing said first magnet Valve, means effective when said first magnet valve is energized for connecting said motor with said firstpipe, a second contact mechanically connected with, the movable element of said first magnet valve in such manner that said second contact will become opened when said first magnet valve becomes, energized, a second magnet valve, means for at times energizing said second. magnet valve when, said second contact is closed, and means eifective when said second magnet valve becomes energized for connecting said motor with said second pipe. HERBERT L. BONE. 

